This invention relates to a coating apparatus and method by which a web of paper or the like may be coated on its opposite sides either with the same or with different coating materials.
Various arrangements have been proposed by which webs may be coated simultaneously on both sides with similar or dissimilar coatings. One such arrangement is described and claimed in the above co-pending application Ser. No. 921,502, which discloses a dual blade type of coater in which a web of paper is moved upwardly between a pair of opposed non-contacting fountains and the excess materials are removed by a pair of co-acting doctor blades. The doctor blades are mounted for pivotal movement about a common axis.
It is desirable in some instances to utilize a conventional roll-type applicator for applying a coating or sizing material to one side of the web. One patent which discloses a roll applicator in a two-sided coater is Wallsten, U.S. Pat. No. 3,899,615 issued Aug. 12, 1975. In Wallsten, the web moves in a generally downwardly direction over a coating roll, from which the web receives one coating. The opposite side of the web is contacted by a coating blade which forms a dam and creates a reservoir above the blade for a coating material.
Such coaters are difficult to operate for a number of reasons. First, the blade-coated side is moving downwardly away from the coater and therefore is not presented as the top side for immediate drying or cooling systems. Secondly, the entire amount of the excess coating must be controlled by the blade alone, which places a severe demand upon the blade and limits the operator's ability to choose coating weights and web speeds. Very light coatig weights, or accurate control of coating weights, is rendered quite difficult. Further, since the paper is exiting the coater in the downward direction, it is difficult to provide a good operator vantage point for observing the coated web as it leaves the blade.